RESPIRATORY HEALTH RISKS FROM TRAFFIC-RELATED AIR POLLUTION (TRAP) IN URBAN SOUTHEAST ASIAN CITIES: A SYSTEMATIC REVIEW OF EPIDEMIOLOGICAL EVIDENCE

Since the mid-twentieth century, rapid urbanization and motorization have fundamentally transformed the
atmospheric landscape of Southeast Asian cities, making traffic-related air pollution (TRAP) a pervasive
environmental health hazard. This systematic review examines epidemiological evidence on associations
between TRAP exposure and respiratory health outcomes among populations in urban Southeast Asia. The
purpose was to synthesize findings on exposure-response relationships, identify vulnerable populations, and
evaluate how exposure assessment methods influence observed health risks. A comprehensive search following
PRISMA guidelines was conducted across Google Scholar, ScienceDirect, PubMed, Web of Science, and
SpringerLink for studies published from 2016 to 2026. Twenty peer-reviewed articles met inclusion criteria,
representing time-series, cross-sectional, cohort, and case-crossover designs. Results show that particulate
matter (PM₂.₅) is the most frequently examined pollutant, consistently associated with increased asthma
exacerbations, pediatric respiratory infections, hospital admissions, and COPD symptoms. Children emerge as
the most vulnerable population, with effect sizes including odds ratios of 7.17 for respiratory infections and
2.2% increased admission risk per 10 μg/m³ PM₂.₅. Exposure assessment methods significantly influence
associations: high-resolution approaches including land-use regression and mobile monitoring capture stronger
exposure-response relationships than conventional fixed-site monitoring. Occupational groups demonstrate
elevated risks, though evidence for elderly populations and roadside residents remains limited. These findings
indicate that TRAP produces measurable respiratory health effects across Southeast Asian urban contexts, with
magnitude dependent on assessment methodology and population susceptibility. The review emphasizes
integrating high-resolution exposure assessment with epidemiological investigation and highlights the need for
prospective cohort studies to guide urban air quality management.